S. 15 Standards for the quality of channels and paths of DSPs
Standards for the quality of channels and paths of the center shall be established by
¨ recommendations of ITU G.821 and G.826 respectively, and in the Ukraine as well,
¨ Guiding normative document ECE 45-074-97 (Steering the normative documents of the Ukraine Communications State Committee of “Digital Transfer Systems”). A similar document in Russia was introduced by Order of the Ministry of Communications of the Russian Federation №92 from 10.08.96
The quality assessment is conducted on the following parameters:
Ø ESR(Errored Second Ratio) = (NES/NS);
Ø SESR(Severely Errored Second Ratio) = (NSES/NS);
Ø BBER(Background Block Error Ratio) = (NBBE/NB).
Here
NES – the number of seconds with errors ES - a matter of seconds, containing one or several of erroneous blocks in the period of readiness for measurement time;
NSES -- the number of seconds strongly affected by errors SES - it is the second, containing 30% of erroneous blocks, or at least one block with serious injuries to the type of failure CA in the period of readiness for measurement time;
NS – the total number of seconds in the period of readiness for measurement timeТmeas (NS = Тmeassec);
NBBE – the number of blocks with background errors BBE in the period of readiness for measurement time;
NB – total number of blocks in the period of readiness for measurement time except for the blocks within the SES .
For the flow of E1 length of the block is 2048 bits (i.e. for one sec is transferred 1000 units).
The period of unavailability begins with the moment of time, after which it should be in a row 10 sec SES and ends the moment of time, after which it should be in a row 10 sec ES.
 |
| Long-term norms comply with the recommendations of the ITU, their implementation can be checked in practice by means of measurements for a long time (more than one month). They are used in the inspection of quality indicators of digital channels and paths of new transmission systems, which previously on the primary network of the country is not taken. Numerical values of these standards are set at the beginning for the reference circuit of the international connections of the long L = 27 500 km (Table. P-15.1) and translated, in the future, on the backbone of the actual length of the LФ of a given area of the primary network (Table. P-15.2). | |
Table. P-15.1
|
Standards for the quality of reference of the international connections L = 27 500 km long
Табл. П-15.2
The value of correction coefficient «A», taking into account the actual length of digital path and area of the primary network of PN.
| Backbone PN | Intrazone PN | ||
| Length LФ Less or equal (km) | С1 | Length LФ Less or equal (km) | С2 |
| 0,004 | 0,015 | ||
| 0,008 | 0,03 | ||
| 0,012 | 0,045 | ||
| 0,016 | 0,06 | ||
| 0,02 | 0,075 | ||
| 0,024 | |||
| 0,028 | |||
| 0,029 |
For digital path РРСП length of less 2500 km value SESR increases in 0.0005, to take account of the adverse conditions of the transfer for the worst month of the year.
| Short-term (operational) standards are Express standards, they have been developed in accordance with the recommendations of ITU M. 2100, M. 2110, M. 2120 and are used for commissioning; while and evaluation of the results of repair. The operational standards are assessed only on the parameters of ESR and SESR. |
In accordance with the ECE 45-074-97 to assess Express measurements
1. Determined the average operational standards
|
where
B (value of operational standards for the reference of the international chain of long-27 500 km) are given in the Table. P-15.1.
D (a part of the operational, operational standards, taking into account the actual length and type of area the primary network is shown in
Table.P-15.3.
k (limit value of the coefficient of quality control), which in accordance with the ECE 45-074-97 to enter CT (CC) in the operation of the chosen equal to 0.5.
Table.P-15.3.